[augmentations] No error if there is metadata named `augmented` in augmentation scope

[sgrekhov]

In an augmentation scope augmented is a reserved world and can be used for calling introductory declaration only. Any other use of this word is a compile-time error. But there is no expected error in the analyzer below:

class augmented {
  const augmented();
}
class C {}

augment class C {
  @augmented()  // There should be an error here but there isn't
  void foo() {}
}

Appropriate co19 test, for example, https://github.com/dart-lang/co19/blob/master/LanguageFeatures/Augmentation-libraries/augmented_expression_A03_t33.dart

[lrhn]

I've been arguing that augmented should only be reserved in places where it can actually mean "invoke the augmented declaration", so only where there can be an expression (function bodies, initializer lists, default value expressions and variable initializer expressions).

I don't remember what was decided about that, if anything.

[eernstg]

The language team decided at the meeting Oct 30 2024 that the currently specified treatment should not change. This implies that augmented inside a declaration marked as augment cannot be used in any other way than as a reference to the augmented declaration (that is, an invocation of the augmented method or getter, or as an evaluation of the augmented initializing expression). In particular:

Inside an expression in an augmenting member declaration, the identifier augmented can be used to refer to the augmented function, getter, or setter body, or variable initializer. This is a contextual reserved word within augment declarations

A compile-time error occurs if a declaration with the basename augmented occurs in a location where any enclosing declaration is augmenting. This error is applicable to all such declarations, e.g., local functions, local variables, parameters, and type parameters.

Consider a non-augmenting member declaration Dm that occurs inside an augmenting type declaration Dt. A compile-time error occurs if the identifier augmented occurs in Dm.

For example, inside augment class C we could have a declaration like void f() {...augmented()...}. This is an error because the outer augment forces the meaning of augmented to be about augmentation in the entire scope, but the method declaration is introductory and hence there is no earlier declaration to augment.

So the error at @augmented() which was mentioned in the original posting should indeed be reported.